1. Field of the Invention
The present invention relates to a condenser microphone having vibration plates and back pole plates. More particularly, the present invention relates to a condenser microphone in which a miniaturization and a high sound quality are realized so as to be preferably used for the sound collection for the stocking in a musical, a drama or the like.
2. Description of Related Art
Higher sound quality and smaller size are required for condenser microphones used, for example, in the sound collection for stocking of the musical, the drama or the like. Most of those kinds of the condenser microphones usually employ a structure as shown in FIG. 1. That is, a vibration plate 1 is placed in parallel to a sound wave plane. The vibration plate 1 adhered on a circular ring 5 and a ring shape spacer 7 are inserted into a cylindrical body 3. Moreover, a back pole part 9 supported by insulating material is inserted. Then, both ends of the body 3 are closed. Accordingly, the vibration plate 1 and a back pole 9a are facing to each other while a predetermined space is maintained.
If the outer diameter of the body 3 becomes minimal, the area of the vibration plate becomes smaller in order to secure the thickness required for the body 3 and the insulator, the space for the adhesive surface to fix the vibration plate 1 and the like. Accordingly, a sensibility is reduced, and an SN ratio is also aggravated.
In view of the above-mentioned circumstances, other types of condenser microphones as shown in FIGS. 2 and 3 are available. The condenser microphone 21 shown in FIG. 2 is configured in such a way that a single rectangular vibration plate 11 adhered on a ring 11a is used, and this vibration plate 11 is sandwiched between a front room 13, a spacer 15, a back pole 17a and a holder 17, and it is accommodated by a body 19. The condenser microphone 33 shown in FIG. 3 is configured in such a way that two circular vibration plates 23, 23 adhered on rings 23a, 23a are used, and each of spacers 25, 25 is interposed between each of the two circular vibration plates 23, 23 and each of back poles 27a, 27a, and a holder 29 is placed oppositely to and sandwiched between the back plates 27a, 27a, and the holder 29 is accommodated by a body 31.